<!doctype html>
<style>
div {
	border: 1px solid red;
	width: 32px;
	height: 32px;
	display: inline-block;
}

#a {
	background: url("black16+4.png") red;
	background: red 20px right; /* invalid position */
	background: left red top; /* invalid: cannot mix values */
	background: red, red; /* invalid: only last layer can have background-color */
}

#b {
	background: 
		url(blue16.png) top left no-repeat, 
		url('green16.png') right top no-repeat,
		url("blue16.png")  100% bottom no-repeat, 
		src("green16.png") 0px bottom no-repeat;  /* this doesn't work in Chrome/Firefox because of src() */
}
</style>

<div id=a></div>
<div id=b></div>